JP2005-299430A discloses an internal combustion engine comprising a first catalyst arranged in an exhaust passage of an engine body and having an oxygen storage ability, a second catalyst arranged in the exhaust passage at the downstream side from the first catalyst and having an oxygen storage ability, a first exhaust sensor (air-fuel ratio sensor) arranged at an upstream side of the first catalyst, a second exhaust sensor (oxygen sensor) arranged between the first catalyst and the second catalyst, and a third exhaust sensor (oxygen sensor) arranged at the downstream side of the second catalyst.
Further, this patent literature discloses a control device of this internal combustion engine controlling the engine body so that the air-fuel ratio of the exhaust detected by the first exhaust sensor becomes a target air-fuel ratio, switching the target air-fuel ratio to a rich air-fuel ratio when judging based on the detection value of the second exhaust sensor that lean air-fuel ratio exhaust is flowing out from the first catalyst, and conversely switching the target air-fuel ratio to a lean air-fuel ratio when judging that rich air-fuel ratio exhaust is flowing out. Further, it discloses to judge that the oxygen storage amount of the second catalyst is near zero when judging based on the detection value of the third exhaust sensor that rich air-fuel ratio exhaust is flowing out from the second catalyst and to correct the target air-fuel ratio so that the target air-fuel ratio becomes larger than normal so as to restore the second catalyst storage amount.